Printed one of these a while back; in yellow, for Scorpion, and printed the caps in black. The black accents were done with Sharpie. I used a Dremel to cut out the front notches/"vents" and use hot-glue to glue a double layer of filter covering those openings, on the inside of the mask. I used a soldering iron and some old print cast-offs to permanently seal the joints where the chin piece folds into the cheek pieces, because the hot-glue joint wasn't holding on one side. I also used some 1/4" wide, stick-on foam gasket on the inside to help with fit and comfort. I used black sash line as a behind-the-neck-over-the-head tie, because I have tonnes of it (from my line of work) and because rubber band behind the ears is painful for me.
I didn't realize when I molded it, that I'd done it crooked. Even with the additional openings, between the hot-glue fill at the nose piece, the foam gasket everywhere, and the double layer of filter everywhere; the fit is snug and secure enough that the mask shifts in and out with my breathing. Love this mask!